cciss_allow_hpsa=1: This option prevents the cciss driver from
attempting to drive any controllers that the hpsa(4) driver is capable
of controlling, which is to say, the cciss driver is restricted by this
option to the following controllers:

When this file is written to, the driver rescans the
controller to discover any new, removed, or modified logical drives.

/sys/bus/pci/devices/<dev>/ccissX/resettable

A value of 1 displayed in this file indicates that the
"reset_devices=1" kernel parameter (used by kdump) is
honored by this controller. A value of 0 indicates that the
"reset_devices=1" kernel parameter will not be honored. Some
models of Smart Array are not able to honor this parameter.

SCSI sequential access devices and medium changer devices are supported and
appropriate device nodes are automatically created (e.g., /dev/st0,
/dev/st1, etc.; see st(4) for more details.) You must enable
"SCSI tape drive support for Smart Array 5xxx" and "SCSI
support" in your kernel configuration to be able to use SCSI tape drives
with your Smart Array 5xxx controller.

Additionally, note that the driver will not engage the SCSI core at init time.
The driver must be directed to dynamically engage the SCSI core via the
/proc filesystem entry, which the "block" side of the driver
creates as /proc/driver/cciss/cciss* at run time. This is because at
driver init time, the SCSI core may not yet be initialized (because the driver
is a block driver) and attempting to register it with the SCSI core in such a
case would cause a hang. This is best done via an initialization script
(typically in /etc/init.d, but could vary depending on distribution).
For example:

Hot plugging of SCSI tape drives is supported, with some caveats. The
cciss driver must be informed that changes to the SCSI bus have been
made. This may be done via the /proc filesystem. For example:

echo "rescan" > /proc/scsi/cciss0/1

This causes the driver to:

1.

query the adapter about changes to the physical SCSI buses
and/or fibre channel arbitrated loop, and

2.

make note of any new or removed sequential access devices
or medium changers.

The driver will output messages indicating which devices have been added or
removed and the controller, bus, target, and lun used to address each device.
The driver then notifies the SCSI midlayer of these changes.

Note that the naming convention of the /proc filesystem entries contains
a number in addition to the driver name (e.g., "cciss0" instead of
just "cciss", which you might expect).

Note: Only sequential access devices and medium changers are presented as
SCSI devices to the SCSI midlayer by the cciss driver. Specifically,
physical SCSI disk drives are not presented to the SCSI midlayer. The
only disk devices that are presented to the kernel are logical drives that the
array controller constructs from regions on the physical drives. The logical
drives are presented to the block layer (not to the SCSI midlayer). It is
important for the driver to prevent the kernel from accessing the physical
drives directly, since these drives are used by the array controller to
construct the logical drives.

The Linux SCSI midlayer provides an error-handling protocol that is initiated
whenever a SCSI command fails to complete within a certain amount of time
(which can vary depending on the command). The cciss driver
participates in this protocol to some extent. The normal protocol is a
four-step process:

*

First, the device is told to abort the command.

*

If that doesn't work, the device is reset.

*

If that doesn't work, the SCSI bus is reset.

*

If that doesn't work, the host bus adapter is reset.

The cciss driver is a block driver as well as a SCSI driver and only the
tape drives and medium changers are presented to the SCSI midlayer.
Furthermore, unlike more straightforward SCSI drivers, disk I/O continues
through the block side during the SCSI error-recovery process. Therefore, the
cciss driver implements only the first two of these actions, aborting
the command, and resetting the device. Note also that most tape drives will
not oblige in aborting commands, and sometimes it appears they will not even
obey a reset command, though in most circumstances they will. If the command
cannot be aborted and the device cannot be reset, the device will be set
offline.

In the event that the error-handling code is triggered and a tape drive is
successfully reset or the tardy command is successfully aborted, the tape
drive may still not allow I/O to continue until some command is issued that
positions the tape to a known position. Typically you must rewind the tape (by
issuing mt -f /dev/st0 rewind for example) before I/O can proceed again
to a tape drive that was reset.

This page is part of release 4.15 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the latest
version of this page, can be found at
https://www.kernel.org/doc/man-pages/.